Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
From time to time, a wireless service provider may build-out a new radio access network (RAN). A new RAN may allow the wireless service provider to provide wireless service in a new market area. Or, the new RAN may allow the wireless service provider to take advantage of a new radio access technology in a market area with an established RAN. For example, a wireless service provider may build out an LTE (Long-Term Evolution) RAN alongside an established CDMA (Code Division Multiple Access) RAN to take advantage of LTE technology.
Build-out of a RAN may involve installation of base stations at various cell sites within a market area. Each base station may be configured to radiate and thereby define one or more coverage areas in which to serve mobile terminals according to a radio access technology. Further, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a mobile terminal within coverage of the RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other mobile terminals served by the base station or by other base stations.
As each new base station is added to the RAN, an identifier is assigned to each coverage area provided by the RAN to differentiate the respective coverage area from other coverage areas within the RAN. In operation, a base station may provide the assigned identifiers of its coverage areas to nearby mobile terminals and base stations within range of air-interface communication by broadcasting its assigned identifiers over an air-interface. Upon receiving a broadcasted identifier, nearby mobile terminals may reference the broadcasted identifier in an attachment or handover request. Other operations are possible as well.
Typically, each radio access technology has an identifier of a different type. For example, CDMA has one type of identifier known as a pseudo-noise (PN) offset while LTE has a different type of identifier known as a Physical Cell ID (PCI). Moreover, each type generally has a limited number of unique identifiers available. For example, there are 512 unique PN offsets to identify assign to coverage areas in a CDMA RAN. In practice, it is common to re-use identifiers within the RAN because of the limited number of unique identifiers available.
Operations such as attachment and handover may be disrupted by an issue known as identifier conflict. Identifier conflict may occur when two or more coverage areas are assigned the same identifier. Assigning the same identifier to coverage areas creates ambiguity among the coverage areas that may cause confusion within the RAN. For example, when a mobile terminal requests handover to a target coverage area that is involved in an identifier conflict, the identifier of the target coverage area represents two or more possible target coverage areas. Since the two or more possible target coverage areas have the same identifier, a base station receiving the handover request may not be able determine which of the two or more possible target coverage areas is the target coverage area and may thereby be unable to successfully resolve the handover.
In practice, assigning identifiers to coverage areas in a manner that geographically isolates coverage areas having the same identifier from one another avoids identifier conflict. However, due to human and computer error in assigning identifiers, identifier conflict remains a recurring problem. Generally, wireless service providers attempt to minimize the occurrence of these issues because an identifier conflict may cause a user to experience dropped calls and other disadvantages.